Glycol dispersion of inorganic powder, process for producing the same, and polyester composition containing the dispersion

ABSTRACT

A glycol dispersion of an inorganic powder is provided, which comprises glycol and an inorganic powder dispersed therein, said inorganic powder being surface-treated with a dispersant having a solubility of not less than 5 (g/100 g-water) in water of 20° C., and which contains water and/or methanol in the specific amounts. According to the present invention, it is not required to transport a slurry of water, methanol or glycol, but possible to transport in the form of powder, so that efficiency in transportation is not only enhanced, but a drastic simplification in the production steps and a cost reduction are attainable because neither a distillation apparatus for replacing a solvent such as water and methanol with glycol nor a step of wet-pulverizing is required. Moreover, a glycol dispersion of the present invention is able to reproduce the excellent shape and size of the inorganic particles before drying or in the initial state and therefore has an excellent dispersibility.

TECHNICAL FIELD

This application is a 371 of PCT/JP98/03139 filed Jul. 14, 1998.

The present invention relates to a glycol dispersion of an inorganicpowder and production method thereof, and a polyester compositioncontaining said dispersion. More particularly, the present inventionrelates to a glycol dispersion of an inorganic powder and productionmethod thereof, and a polyester composition containing said dispersion,which attain simplification of production steps, reduction oftransportation cost and prevention of breakage of inorganic particles ina method for dispersing an inorganic powder in glycol such as ethyleneglycol in an attempt to improve a coefficient of friction and hue of apolyester, and to impart opacity and micropores to a polyester, which isfor use in film or fiber, in particular.

BACKGROUND ART

Nowadays, polyester produced industrially, especiallypolyethyleneterephthalate has excellent physical and chemicalcharacteristics and thus has been widely used as fiber, film and othermolded articles. In such a polyester composition, it has beenconventionally carried out to cause fine particles to be contained inpolyester in order to improve a coefficient of friction and hue ofpolyester and to impart opacity and micropores to polyester.

For example, in the case of reducing a coefficient of friction, it isknown that since polyester is inferior in slipperiness in molding andprocessing steps as well as in handling of products, troubles such asdeterioration in workability and commercial value arise, in spite of itsexcellent characteristics. Most of such causes come from a highcoefficient of friction of polyester itself. As a measure to thesetroubles, many methods are proposed and put into practice which allowfine particles to be contained in polyester to thus impart appropriateuneveness to the surface of a molded article so that surface smoothnessof the molded article is improved.

As means of improving the surface characteristics of polyester, thefollowing two methods have been known:

(1) a method for separating out a part or whole of a catalyst or thelike used for the synthesis of polyester in the reaction process(internal particle separating-out method), and

(2) a method for adding fine particles such as calcium carbonate andsilicon dioxide in the course of or after polymerization (externalparticle adding method).

However, the internal particle separating-out method (1) has a drawbackof having difficulty in controlling the amount and size of particles andin preventing the formation of coarse particles because in this methodparticles are to be formed during reaction, though the affinity betweenpolyester and particles is somewhat good, for such particles consist ofa metallic salt of a polyester component.

The external particle adding method (2), which consists in adding fineparticles of an inorganic compound insoluble in and inert to polyestersuch as titanium dioxide, silica, talc, kaolin and calcium carbonateduring or after polymerization, is superior to the method (1) describedabove with regard to the improvement of sliding property, if theparticle size and the amount of addition of the inorganic compound areproperly selected and coarse particles are removed by classification orthe like in advance.

Also, for the improvement of dispersibility in polyester of such fineparticles of an inorganic compound there is proposed a method ofpreparing a glycol slurry of fine particles of an inorganic compound andadding it in the process of the polyester manufacture, but there issomething to be desired about the dispersibility as well as long-termdispersion stability of such fine particles of an inorganic compound inglycol, hence, when the glycol with such fine particles of an inorganiccompound suspended therein is stored for a long period of time, thereare problems that such fine particles of an inorganic compoundprecipitate to form hard cakes which are difficult to redisperse, andthat fine particles of such inorganic compound agglomerate in glycol orin the course of manufacture of polyester. The presence of agglomeratedcoarse particles in polyester causes yarn breakage in the spinningprocess, formation of the so-called “fish eye” and, in particular,drop-out or lowering of S/N ratio when it is used for the manufacture offilm for magnetic tape.

As the particles having a high dispersibility used such uses, vateritecalcium carbonate, spherical silica prepared by a sol-gel method,calcite cubic calcium carbonate may be exemplified. Those are producedby a high technique so that individual particles may be present withoutaggregation. Those are usually prepared in water or alcohol and it isnecessary to prepare a slurry of the monodispersed particles and glycolby substituting water or alcohol with glycol while maintaining a highdispersion. For this purpose, a vacuum distiller such as an evaporatoris used but this method is high expensive. Moreover, even when theglycol slurry prepared in this way is transported to a place wherepolyester is produced, or even when a slurry containing water ormethanol is transported to a production place of polyester and distilledtherein, there is not a bit of difference between the two in that thetransportation is made in the form of slurry so that a decrease intransportation efficiency and an increase in transportation cost are notavoidable.

In order to solve those problems, it is considered to obtain a powder bydrying the particles monodispersed in water or methanol by the use of adryer such as a spray dryer, and to mix the powder with glycol to thusprepare a glycol slurry. However, the monodispersed particles, whendried, form aggregates and therefore the monodispersed particlesprepared in this method are not redispersed in glycol in good dispersionstate of the original particles.

Moreover, Japanese Patent Examined Publication No. 2-48174 proposes amethod for obtaining good dispersibility by wet-pulverizing in glycol aprecipitated calcium carbonate having the specific dispersibility andparticle size under the specific conditions. Although this method issaid to be good in uses in which ununiformity of the particle shape inglycol dispersion is not problematic, it is not suitable for sphericalor cubic monodisperse calcium carbonate having the uniform shape andparticle size.

Although, for example, a glycol dispersion having a good dispersibilityis obtained if spherical calcium carbonate or silica obtained by a spraydryer is used in the form of powder as a wet-pulverizing material andits glycol slurry is wet-pulverized according to the method described inthe above publication, a cost is not only increased since thewet-pulverizing step is added, but the shape is irregular due to thepulverization and the original shape is lost. In addition, unintendedfine particles occasionally generate due to the pulverization and theyreaggregate to form coarse particles in the production step ofpolyester, which deteriorates the physical properties of thecomposition. Furthermore, in the method described in the publication,fragments of a medium such as glass used for the pulverization aremingled into the pulverized matters. The fragments are usually coarseparticles of 10 to 100 μm and thus this method is not suitable for filmof polyester or the like.

As stated above, it is difficult to prepare a glycol dispersion bydispersing an inorganic powder in glycol while maintaining its shape andparticle size before drying or in the initial state. Therefore, it isimpossible to transport inorganic particles in the form of powder forthe purpose of reducing a transportation cost and for this reason, thetransportation in the form of slurry is forced, otherwise, even when thetransportation in the form of powder is possible, it is very expensiveto prepare a glycol slurry of satisfactory dispersion from this powder.

In light of the foregoing situation, the present invention provides amethod for producing a glycol dispersion which is not only capable of adrastic simplification in the production steps and a reduction in costby omitting the use of an distillation apparatus for substituting asolvent such as water and methanol with glycol, requiring neithertransportation of water, methanol or glycol slurry nor awet-pulverization step, but capable of dispersing an inorganic powder inglycol with maintaining its particle shape and particle size beforedrying or in the initial state, and further provides a polyestercomposition containing the glycol dispersion of the inorganic powderuniformly dispersed in glycol.

DISCLOSURE OF THE INVENTION

The present inventors have made an extensive series of studies in anattempt to solve the above problems and have found out that a glycoldispersion is obtained which not only has an excellent dispersibility,but realizes a reduction in transportation cost, simplification ofproduction steps and the maintenance of the particle shape and size, byusing an inorganic powder surface-treated with a dispersant having aspecific range of solubility and adding a small amount of water and /ormethanol adjusted in an amount and a concentration so as to satisfy thespecific conditions, and that a polyester composition having anexcellent performance is provided by using the glycol dispersion infilms, fibers and molded articles, thus completed the present invention.

The present invention is, in a first aspect, to provide a glycoldispersion of an inorganic powder which comprises glycol and aninorganic powder dispersed therein, said inorganic powder beingsurface-treated with a dispersant having a solubility of not less than 5(g/100 g-water) in water of 20° C., and which contains water and/ormethanol in a range to satisfy the following equations (1) to (3):

1≦A≦20/t  (1)

0.5≦B≦10  (2)

5≦C  (3)

wherein

A: % by weight of water and/or methanol based on the inorganic powder,

t: % by weight of the dispersant based on the inorganic powder,

B: % by weight of water and/or methanol in the glycol dispersion,

C: % by weight of the inorganic powder in the glycol dispersion.

The present invention is, in a second aspect, to provide a method forproducing a glycol dispersion of an inorganic powder which comprises thefollowing steps of:

surface-treating an inorganic powder with a dispersant having asolubility of not less than 5 (g/100 g-water) in water of 20° C., and

dispersing the surface-treated inorganic powder in glycol together withwater and/or methanol so as to satisfy the following equations (1) to(3):

1≦A≦20/t  (1)

0.5≦B≦10  (2)

5≦C  (3)

wherein

A: % by weight of water and/or methanol based on the inorganic powder,

t: % by weight of the dispersant based on the inorganic powder,

B: % by weight of water and/or methanol in the glycol dispersion,

C: % by weight of the inorganic powder in the glycol dispersion.

The present invention is, in a third aspect, to provide a polyestercomposition containing the above-mentioned glycol dispersion of aninorganic powder.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic illustration of an apparatus usable for themeasurement of a coefficient of friction of a film.

BEST MODE FOR CARRYING OUT THE INVENTION

As the inorganic powder usable in the present invention, there is nospecific limitation if it is usually usable for a polyester, such astitanium dioxide, silica, alumina, kaolin, talc, calcium carbonate andcalcium phosphate (apatite etc.). Among those, titanium dioxide, silica,talc, kaolin, calcium carbonate and calcium phosphate are preferable,and a spherical silica and a hexahedron precipitated calcium carbonatewhich are nearly in a state of monodispersion at the time of preparationare most preferable, from the viewpoint that a glycol dispersion isprepared without breakage of the particle shape. These may be usedsingly or in combination of two or more.

As the average particle size of the inorganic powder, there is nospecific limitation if it is usually added to a polyester film or fiber,but the range of 0.01 to 15 μm is preferable, the range of 0.05 to 5 μmis more preferable, and the range of 0.05 to 2 μm is most preferablefrom the viewpoint of being appropriate fine particles and a gooddispersion state being kept. In the case of too fine particles,dispersibility of the particles tends to be prevented, and in the caseof too coarse particles, the particles tend to precipitate in a glycolslurry or to damage the smoothness of the suface of a polyester.

The dispersant with which the inorganic particles are surface-treated isrequired to have a solubility of not less than 5 (g/100 g-water) inwater of 20° C., preferably not less than 20, more preferably not lessthan 50. That is because a high solubility to water is desirous since itneed to be dissolved rapidly in an extremely small amount of water to beadded.

As the dispersant, there are included alkali metal salts of condensedphosphoric acids such as potassium tripolyphosphate and sodiumhexametaphosphate; alkali metal salts of alicyclic or aromatic resinacids such as abietic acid, neoabietic acid, benzoic acid and cinnamicacid; sulfonic acid compounds such as alkylsulfonic acid and alkylbenzene sulfonic acid; sulfuric acid compounds such as alkylsulfuricacid and alkyl ether sulfuric acid; phosphoric acid compounds such asalkylphosphoric acid and alkyl ether phosphoric acid; esters such asmethyl ester, ethyl ester and hexyl ester, or salts of alkali metals,ammonium and amine of those acid compounds; cellulose compounds such ashydroxyethyl cellulose and carboxymethylcellulose; unsaturatedcarboxylic acids such as acrylic acid, methacrylic acid and maleic acid,and polymers thereof; copolymers of those unsaturated carboxylic acidsand monomers copolymerizable therewith such as alkyl acrylates, alkylmethacrylates, acrylates and methacrylates having alkoxy groups,polyalkyleneglycol monoacrylates and methacrylate vinyl esters, partialor complete neutralized substances such as alkali metal, ammonium andamine salts of those copolymers. These may be used singly or incombination of two or more.

The amount of the dispersant treated is not limited in particular, butis usually 0.01 to 10 parts by weight, preferably 0.01 to 5 parts byweight based on 100 parts by weight of the inorganic powder. If it isless than 0.01 parts by weight, the surface-treated effect is notsufficient, and if it is more than 10 parts by weight, besides beinguneconomical, the polymerization is occasionally prevented.

As the method for surface-treating the inorganic powder with thedispersant, any method conducted conventionally may be used. Forexample, in the case of an inorganic powder such as ground calciumcarbonate, kaolin and talc which are produced by a dry-pulverization,the dispersant may be adsorbed onto the surface of the inorganic powderby the use of a mixer such as a Super Mixer, or the inorganic powder maybe suspended in water or alcohol into which the dispersant may be mixedin a predetermined amount, followed by drying by the use of a dryer suchas a spray dryer. In the case of an inorganic powder such as aprecipitated calcium carbonate, which is synthesized in an aqueoussystem, it may be obtained as a powder, then subjected to the above drytreatment, but it is advantageous in cost to add the dispersant to asuspension immediately after reaction or a condensed liquid thereof,followed by drying. Moreover, since it is possible to reproduce thedispersion before drying of an inorganic powder according to the presentinvention and thus the inorganic powder may also be prepared asparticles having the dispersibility near to a single particle, or mayalso be adjusted advantageously to the desired particle size, ifnecessary, by a wet-pulverization or the like. In this case, thedispersant may be added at any time without damaging the effects of thepresent invention, if an inorganic powder is in a state of an aqueousslurry.

The inorganic powder surface-treated with the dispersant is dried andpulverized by an ordinary method to thus obtain the inorganic powder ofthe present invention.

As the glycol in which the inorganic powder surface-treated with thedispersant preliminarily is dispersed, aliphatic glycols having a carbonnumber of 2 to 10 such as ethylene glycol, trimethylene glycol,tetramethylene glycol, pentamethylene glycol, hexamethylene glycol anddecamethylene glycol; alicylic diols such as cyclohexanedimethanol;aromatic diols such as 2,2′-bis (4-hydroxyphenyl) propane andhydroquinone are exemplified. These may be used singly or in combinationof two or more.

The method for dispersing the inorganic powder in glycol ischaracterized in that a trace amount of water and/or methanol iscontained when the inorganic powder and glycol are mixed, and that theamount of water and/or methanol should satisfy the specific equations asdescribed below.

First, in the equation (1), the amount A (% by weight) of water and/ormethanol satisfying 1≦A≦20/t based on the amount t (% by weight) of thedispersant based on the inorganic powder is determined. If A is lessthan 1, the amount of water and/or methanol does not arrive at a levelenough for the dispersant to achieve its function to thus cause adecrease in dispersibility, inversely, if A is more than 20/t, theamount of water and/or methanol at the time of polymerization increasesexcessively to thus cause hydrolysis of a polyester or bumping in thepolymerization of a polyester.

Second, in the equation (2), the amount B (% by weight) of water and/ormethanol in the glycol dispersion is determined in a range of 0.5 to 10.If it is less than the lower limit, the function of the dispersant isnot provided, inversely, if it is more than the upper limit, the sameundesirable phenomenon as in the equation (1) occur.

Third, in the equation (3), the amount C (% by weight) of the inorganicpowder contained in the glycol dispersion, i.e., the solid concentrationis adjusted to not less than 5. If it is less than 5, a sufficient shearis not imposed on the individual particles to thus cause a decrease indispersibility. For this reason, the solid concentration should be madeas high as possible, preferably not less than 30, more preferably notless than 40. After the glycol dispersion is prepared once, it may beadjusted with glycol to the desired concentration.

When the glycol dispersion is prepared, water and methanol may be usedconjointly. If the solubility in water of a dispersant is not less than5 and the solubility in methanol is also not less than 5, the amount ofwater added may be further reduced, and in some cases the dispersion ispossible without addition of water.

Moreover, attention is called to water (and/or methanol) adsorbed to aninorganic powder when water and/or methanol is added. The amount ofwater (and/or methanol) in the above equations naturally contains water(and/or methanol) adsorbed.

In dispersing a glycol slurry added with water and/or methanol, the useof a pulverizer using a medium such as a Sand Grinder Mill is notnecessary and the glycol dispersion of the present invention is obtainedif mixed sufficiently by the use of an ordinary stirrer, but it may, ifnecessary, be further subjected to the adjustment of the particle sizeby the use of a wet-pulverizer, an impact-type high pressure disperser,a supersonic wave disperser or the like, and thereafter, may besubjected, if necessary, to the removal of coarse particles by the useof a filter having a pore size of approximately 10 μm or less, a superdecanter or the like. In this method, the glycol dispersion maintainingthe particle shape and size of the inorganic powder before drying or inthe initial state is obtained.

The glycol dispersion is blended with a polyester to obtain a polyestercomposition.

As the polyester, there may be exemplified polyesters comprisingaromatic dicarboxylic acids as the main acid component and aliphaticglycols, alicyclic diols and aromatic diols as the main glycolcomponent.

As the aromatic dicarboxylic acid, for example, terephthalic acid,naphthalenedicaboxylic acid, isophthalic acid,diphenylethanedicarboxylic acid, diphenyldicarboxylic acid,diphenyletherdicarboxylic acid, diphenylsulfonedicarboxylic acid,diphenylketonedicarboxylic acid and anthracenedicarboxylic acid areexemplified. These may be used singly or in combination of two or more.As the polyester comprising these as the main components, polyestershaving, for example, alkyleneterephthalate and/or alkylenenaphthalate asits main component are preferably used.

The amount of the glycol dispersion added to a polyester is notdetermined unconditionally, depending on the kind or use of thepolyester, but in the case of a polyester film, the range of 0.005 to 3parts by weight in terms of an inorganic powder is appropriate, and therange of 0.01 to 1 part by weight in terms of an inorganic powder ispreferable, based on 100 parts by weight of a polyester resin. If it isless than the lower limit, the intended effect is not sufficient, sincethe amount added is not only scanty, but the accuracy of uniformlydispersing it into the polyester resin lowers, inversely, if it is morethan the upper limit, the physical properties are not improved inproportion to the amount added and inconveniences such as a decrease instretching property take place.

The polyester obtained from the polyester composition of the presentinvention is suited to fibers and films, in particular, to films for usein videotapes, audiotapes, condensers, photo resists, packages forfoods, prepaid cards or the like, in which excellent anti-blockingeffect as well as electric properties is required.

Hereinafter, the present invention will be explained in more detail byway of examples and comparative examples, by which the present inventionis in no way limited.

With respect to the evaluation, the particle size distributions of awater slurry before drying and a glycol dispersion are measured by themethod as set forth below for observing the dispersion reproducibilityof a glycol dispersion. As a synthetic resin, apolyethyleneterephthalate film is made and evaluated for the propertiesas set forth below.

Measurement of the Particle Size Distribution

Measuring device: MICROTRAC FRA manufactured by Leeds & Northrup

Solvent: Ethylene glycol

Specimen: Into 50 cm³ of a solvent, 2 to 3 g of a water slurry beforedrying or a glycol dispersion are added and stirred adequately.

The results obtained by the above-mentioned methods are compared withrespect to the following properties:

D10: Particle size (μm) accounting for 10% by weight as measured fromthe larger particle size side in the particle size distribution measured

D50: Particle size (μm) accounting for 50% by weight as measured fromthe larger particle size side in the particle size distribution measured

D90: Particle size (μm) accounting for 90% by weight as measured fromthe larger particle size side in the particle size distribution measured

D10/D90: Indication showing variability in the particle sizedistribution. As the value becomes closer to 1, the particle sizedistribution becomes sharper.

5 μm<: weight % of coarse particles of more than 5 μm in the particlesize distribution measured Production of polyethyleneterephthalate film:

Ethylene glycol dispersions described in Tables 1 to 3 were added priorto a polyesterification, followed by a polyesterification reaction, tothus obtain polyethyleneterephthalates containing 0.1% by weight of theparticles and having a limiting viscosity number (orthochlorophenol, 35°C.) of 0.62 dl/g. The polyethyleneterephthalates were dried at 160° C.,followed by a melt extrusion at 290° C., rapidly cooled and solidifiedon a casting drum having a temperature maintained at 40° C., to therebyobtain unstretched films. The thus obtained unstretched films werepre-heated at 70° C. by a heating roller, stretched 3.6 times to thelongitudinal direction while heating with an infrared heater, and thenstretched 4.0 times to the lateral direction at 90° C., followed by heattreatment at 200° C. Thus, biaxially oriented films having a thicknessof 15 μm were obtained.

The quality of the thus obtained films was evaluated according to thefollowing methods.

{circle around (1)} Surface Roughness of the Film(Ra)

The surface roughness of the film is a value defined as a center lineaverage height (Ra) of JIS-B0601. In the present invention, a tracertype surface roughness tester of Kosaka Kenkyusho Co., Ltd., (SURFCORDERSF -30C) was used to measure the center line average height. Measuringconditions are as follows:

(a) Radius of a head of the tracer: 2 μm,

(b) Measuring pressure: 30 mg,

(c) Cut off: 0.25 mm,

(d) Length for measurement: 0.5 mm, and

(e) An average value is calculated from 4 data obtained by excluding thehighest value from 5 repeated values on the same sample.

{circle around (2)} Friction Coefficient of the Film (μk)

The friction coefficient is measured by using an apparatus shown in FIG.1. In FIG. 1, each number shows parts of the apparatus, respectively, asfollows: 1: unwinding reel; 2: tension controller; 3,5,6,8,9 and 11:free roller; 4: tension detector (inlet); 7: fixing bar (outerdiameter:5 mm) made of stainless steel net, SUS304; 10: tension detector(outlet); 12: guide roller; and 13: winding reel.

Under conditions of a temperature of 20 and a humidity of 60%, a filmcut to ½ inch width was contacted with the fixing bar 7 (surfaceroughness: 0.3 μm) at an angle of θ=(152/180)π radian (152°) and moved(frictioned) at a rate of 200 cm per minute. When the tension controlleris adjusted so that the inlet tension T1 is 35 g, the outlet tension(T2:g) is detected by the outlet tension detector after 90 meter run ofthe film. The traveling friction coefficient pk is calculated from thefollowing equation:

μk=(2.303/θ)log(T 2/T 1)=0.86 log(T 2/35)

{circle around (3+L )} Evaluation of Abrasion-I

A surface of the film of ½ inch width is contacted with a stainlesssteel fixing pin (surface roughness 0.58 μm) having a diameter 5 mm atan angle of 150°, and the fixing pin is moved and frictionedreciprocally about 15 cm intervals at a rate of 2 meters per minute. Inthis case, the inlet tension T1 is 60 g.

The above operations are repeated, and after 40 reciprocal movements, adegree of scratches raised on the surface of the film is visuallyexamined. The evaluation of the scratches is conducted according to thefour-rank criteria:

<Four-rank Criteria>

a: Scratches are scarcely found.

b: A few scratches are found.

c: A considerably many scratches are found.

d: Scratches are found all over the surface.

{circle around (4)} Evaluation of Abrasion-II

Shavingness of the running surface of the film is evaluated by using a 5layered minisuper calender. The calendar is comprised of 5 layered ofNylon rolls and steel rolls. A treatment temperature is 80 and a linearload on the film is 200 kg/cm. A film speed is 50 meters/minute. Afterrunning of 4000 meters in total, the shavingness of the film isevaluated by the three-rank criteria by smudge adhered to the top rollof the calender.

<Three-rank Criteria>

a: No smudge on the roll

b: Little smudge on the roll

c: Smudge on the roll

{circle around (5)} Number of Coarse Protrusions on the Film Surface

After aluminum is thinly vapor deposited on the film surface, the numberof coarse protrusions with four or more quartet circles (number per 1mm² of the measuring area) is counted by using a binary beaminterference microscope, and ranked according to the number of thecoarse protrusions:

1st class: not less than 16; 2nd class: 12-15;

3rd class: 8-11; 4th class: 4-7; and

5th class: 0-3

Method for preparing inorganic particles U, V, W used in examples andcomparative examples:

Inorganic Particles U

100 liters of an aqueous sodium carbonate solution having a 1.0mol/liter concentration (X solution), 100 liters of an aqueous calciumchloride solution having a 0.9 mol/liter concentration (Y solution) andan aqueous sodium hydroxide solution having a 0.03 mol/literconcentration (Z solution) were prepared, respectively.

The X solution and the Z solution were mixed and controlled to 19° C.Into the mixed solution, the Y solution controlled to 17° C. was addeddropwise. The mixed (reacted) solution had the pH 12 and the pH valuewas lowered to 9 by repeating dehydration and washing with servicewater, followed by condensation to thus obtain inorganic particles Umade of a precipitated calcium carbonate.

The calcium carbonate obtained was observed by an electron microscopeand found to be hexahedron particles having an average particle size of1.6 μm. The particle size distribution is shown in Tables 1 and 2.

Using the inorganic particles obtained, the procedures described inExamples 1, 3 and Comparative Examples 1 to 3 as will be described laterwere carried out to thus form glycol dispersions. Inorganic particles V:

Inorganic particles V made of a precipitated calcium carbonate wereobtained in the same manner as in the inorganic particles U, except thatthe concentrations of the X, Y and Z solutions were changed to 1.5mol/liter, 1.4 mol/liter, 0.04 mol/liter, respectively.

The calcium carbonate obtained was observed by an electron microscopeand found to be hexahedron particles having an average particle size of0.5 μm. The particle size distribution is shown in Tables 1 and 2.

Using the inorganic particles obtained, the procedures described inExamples 2, 9 and Comparative Example 4 as will be described later werecarried out to thus form glycol dispersions. Inorganic particles W:

Using a commercially available titanium oxide (average particle size:0.7 μm), a water slurry having a solid concentration of 50% by weightwas formed and wet-pulverized by the use of a wet-pulverizer (DYNO®-MILLmanufactured by WAV Corp.) to thus obtain inorganic particles W made oftitanium oxide having an average particle size of 0.4 μm. The particlesize distribution is shown in Table 3.

Using the inorganic particles obtained, the procedures described inExample 4 and Comparative Example 5 as will be described later werecarried out to thus form a glycol dispersion.

EXAMPLE 1

By repeating dehydration and washing with water of the above-mentionedinorganic particles U by the use of a centrifugal dehydrator, a waterslurry having a solid concentration of 50% by weight was obtained, thento the slurry, 0.4% by weight of a sodium polyacrylate (solubility inwater: 900) was added and mixed, followed by drying by the use of aspray dryer to thus obtain an inorganic powder surface-treated with thedispersant. In dispersing the inorganic particles in glycol, water andethylene glycol in amounts described in Table 1 were added to prepare anethylene glycol slurry having a solid concentration of 62% by weight.The ethylene glycol slurry obtained was stirred for 30 minutes by theuse of a stirrer having a disc type stirring blade to thus obtain anethylene glycol dispersion.

The particle size distribution of the glycol dispersion obtained isshown in Table 1, from which it is understood that the particle sizedistribution before drying was maintained and reproduced.

EXAMPLE 2

By repeating dehydration and washing with water of the above-mentionedinorganic particles V by the use of a centrifugal dehydrator, a waterslurry having a solid concentration of 30% by weight was obtained, thento the slurry, 1.2% by weight of a sodium salt of an acrylicacid-polyethylene glycol monomethacrylate copolymer (weight ratio: 7/3)(solubility in water: 150) were added and mixed, followed by drying bythe use of a spray dryer to thus obtain an inorganic powdersurface-treated with the dispersant. In dispersing the inorganicparticles in glycol, water and ethylene glycol in amounts described inTable 1 were added to prepare an ethylene glycol slurry having a solidconcentration of 50% by weight. The ethylene glycol slurry obtained wasstirred for 30 minutes by the use of a stirrer having a disc typestirring blade to thus obtain an ethylene glycol dispersion .

The particle size distribution of the glycol dispersion obtained isshown in Table 1, from which it is understood that the particle sizedistribution before drying was maintained and reproduced.

EXAMPLE 3

An ethylene glycol dispersion having a solid concentration of 70% byweight was obtained in the same manner as in Example 1, except that theamounts of water and ethylene glycol were changed as shown in Table 1.

The particle size distribution of the glycol dispersion obtained isshown in Table 1, from which it is understood that the particle sizedistribution before drying was maintained and reproduced.

EXAMPLE 4

To a 50% by weight water slurry of the above-mentioned inorganic powderW, 0.7% by weight of a sodium hexametaphosphate (solubility in water:70) was added and mixed, followed by drying by the use of a spray dryerto thus obtain an inorganic powder surface-treated with the dispersant.In dispersing the inorganic particles in glycol, water and ethyleneglycol in amounts described in Table 3 were added to prepare an ethyleneglycol slurry having a solid concentration of 50% by weight. Theethylene glycol slurry obtained was stirred for 30 minutes by the use ofa stirrer having a disc type stirring blade to thus obtain an ethyleneglycol dispersion.

The particle size distribution of the glycol dispersion obtained isshown in Table 3, from which it is understood that the particle sizedistribution before drying is maintained and reproduced.

Comparative Example 1

An ethylene glycol dispersion having a solid concentration of 50% byweight was obtained in the same manner as in Example 1, except that theamounts of water and ethylene glycol were changed as shown in Table 2.

The particle size distribution of the glycol dispersion obtained isshown in Table 2, from which it is understood that the particle sizedistribution is greatly different from that before drying.

Comparative Example 2

An ethylene glycol dispersion having a solid concentration of 15% byweight was obtained in the same manner as in Example 1, except that theamounts of water and ethylene glycol were changed as shown in Table 2.

The particle size distribution of the glycol dispersion obtained isshown in Table 2, from which it is understood that the particle sizedistribution is greatly different from that before drying.

Comparative Example 3

An ethylene glycol dispersion having a solid concentration of 45% byweight was obtained in the same manner as in Example 1, except that theamounts of water and ethylene glycol were changed as shown in Table 2.

The particle size distribution of the glycol dispersion obtained isshown in Table 2. As is apparent from Table 2, the particle sizedistribution before drying was maintained and reproduced, but because ofa large amount of water contained in the glycol dispersion, an excellentfilm was not obtained from the glycol dispersion, as shown bycomparative example that will be described later.

Comparative Example 4

A 50% by weight water slurry of the above-mentioned inorganic particlesV was prepared in the same manner as in Example 2, then to the slurry,3.0% by weight of a sodium oleate (solubility in water: 2) were addedand mixed, followed by drying and pulverizing to thus obtain aninorganic powder surface-treated with the dispersant. In dispersing theinorganic particles in glycol, water and ethylene glycol in amountsdescribed in Table 2 were added to prepare an ethylene glycol slurryhaving a solid concentration of 30% by weight. The ethylene glycolslurry obtained was stirred for 30 minutes by the use of a stirrerhaving a disc type stirring blade to thus obtain an ethylene glycoldispersion.

The particle size distribution of the glycol dispersion obtained isshown in Table 2, from which it is understood that the particle sizedistribution is greatly different from that before drying.

Comparative Example 5

An inorganic powder surface-treated was prepared by changing thedispersant to 2.0% by weight of hexanoic acid (solubility in water: 1)and drying and pulverizing. In dispersing the inorganic particles inglycol, water and ethylene glycol in amounts described in Table 3 wereadded to prepare an ethylene glycol slurry having a solid concentrationof 60% by weight. The ethylene glycol slurry obtained was stirred for 30minutes by the use of a stirrer having a disc type stirring blade tothus obtain an ethylene glycol dispersion.

The particle size distribution of the glycol dispersion obtained isshown in Table 3, from which it is understood that the particle sizedistribution is greatly different from that before drying.

EXAMPLE 9

By repeating dehydration and washing with water of the above-mentionedinorganic particles V by the use of a centrifugal dehydrator, a waterslurry having a solid concentration of 30% by weight was obtained, thento the slurry, 1.1% by weight of an amine salt of an acrylicacid-polyethylene glycol monomethacrylate copolymer (weight ratio: 7/3)(solubility in water: 100) was added and mixed, followed by drying bythe use of a spray dryer to thus obtain an inorganic powdersurface-treated with the dispersant. In dispersing the inorganicparticles in glycol, water and ethylene glycol in amounts described inTable 3 were added to prepare an ethylene glycol slurry having a solidconcentration of 45% by weight. The ethylene glycol slurry obtained wasstirred for 30 minutes by the use of a stirrer having a disc typestirring blade to thus obtain an ethylene glycol dispersion.

The particle size distribution of the glycol dispersion obtained isshown in Table 3, from which it is understood that the particle sizedistribution before drying was maintained and reproduced.

TABLE 1 Inorganic particles U Inorganic particles V Water slurry D10(μm) 2.08 0.80 (before D50 (μm) 1.59 0.51 drying) D90 (μm) 1.20 0.34D10/D90 1.73 2.35 5 μm< (%) 0 0 Example 1 Example 3 Example 2 DispersantKind Sodium polyacrylate Sodium salt of acrylic acid-polyethylene glycolmonomethacrylate copolymer Solubility 900 150 Amount treated t (%) 0.41.2 X (%) 6.0 3.3 1.5 Y (%) 0.2 0.2 0.5 Z (%) 31.8 26.5 48.0 Kind of XWater Water Water 20/t 50 16.67 Glycol A (%) 10.0 5.0 4.0 dispersion B(%) 6.2 3.5 2.0 C (%) 62 70 50 D10 (μm) 2.10 2.05 0.70 D50 (μm) 1.591.59 0.48 D90 (μm) 1.20 1.19 0.33 D10/D90 1.75 1.72 2.12 5 μm< (%) 0 0 0A: % by weight of water and/or methanol based on the inorganic powder t:% by weight of the dispersant based on the inorganic powder B: % byweight of water and/or methanol in the glycol dispersion C: % by weightof the inorganic powder in the glycol dispersion X: % by weight of waterand/or methanol added into a glycol dispersion Y: % by weight of wateradsorbed onto an inorganic powder Z: % by weight of ethylene glycoladded into a glycol dispersion

TABLE 2 Inorganic particles U Inorganic particles V Water slurry D10(μm) 2.08 0.80 (before D50 (μm) 1.59 0.51 drying) D90 (μm) 1.20 0.34D10/D90 1.73 2.35 5 μm< (%) 0 0 Comp. Ex. 1 Comp. Ex. 2 Comp. Ex. 3Comp. Ex. 4 Dispersant Kind Sodium polyacrylate Sodium oleate Solubility900 2.0 Amount treated t (%) 0.4 3.0 X (%) 0.05 0.1 26.8 2.6 Y (%) 0.20.2 0.2 0.4 Z (%) 49.75 84.7 28.0 47.0 Kind of X Water Water Water Water20/t 50 6.67 Glycol A (%) 10.0 5.0 5.0 6.0 dispersion B (%) 6.2 3.5 3.53.0 C (%) 62 70 70 50 D10 (μm) 2.10 2.05 2.05 43.94 D50 (μm) 1.59 1.591.59 0.59 D90 (μm) 1.20 1.19 1.19 0.34 D10/D90 1.75 1.72 1.72 129.23 5μm< (%) 0 0 0 32.15 A: % by weight of water and/or methanol based on theinorganic powder t: % by weight of the dispersant based on the inorganicpowder B: % by weight of water and/or methanol in the glycol dispersionC: % by weight of the inorganic powder in the glycol dispersion X: % byweight of water and/or methanol added into a glycol dispersion Y: % byweight of water adsorbed onto an inorganic powder Z: % by weight ofethylene glycol added into a glycol dispersion

TABLE 3 Inorganic particles W Inorganic particles V Water slurry D10(μm) 0.51 0.82 (before D50 (μm) 0.36 0.53 drying) D90 (μm) 0.25 0.34D10/D90 2.04 2.41 5 μm< (%) 0 0 Example 4 Example 5 Example 9 DispersantKind Sodium hexameta Hexanoic acid Amine salt of acrylic phosphateacid-polyethylene glycol monomethacrylate copolymer Solubility 70 lessthan 1.0 100 Amount treated t (%) 0.7 2.0 1.1 X (%) 4.6 3.6 4.0 Y (%)0.4 0.4 0.5 Z (%) 45.0 36.0 50.5 Kind of X Water Water Water 20/t 28.5710.0 18.18 Glycol A (%) 10 6.67 10 dispersion B (%) 5.0 4.0 4.5 C (%) 5060 45 D10 (μm) 0.62 17.15 0.82 D50 (μm) 0.39 0.55 0.54 D90 (μm) 0.280.33 0.33 D10/D90 2.21 51.97 2.48 5 μm< (%) 0 22.10 0 A: % by weight ofwater and/or methanol based on the inorganic powder t: % by weight ofthe dispersant based on the inorganic powder B: % by weight of waterand/or methanol in the glycol dispersion C: % by weight of the inorganicpowder in the glycol dispersion X: % by weight of water and/or methanoladded into a glycol dispersion Y: % by weight of water adsorbed onto aninorganic powder Z: % by weight of ethylene glycol added into a glycoldispersion

EXAMPLES 5 TO 8 AND 10

Using the ethylene glycol dispersions prepared in Examples 1 to 4 and 9,polyester films were prepared in the above-mentioned manner andproperties were evaluated. The results are shown in Table 4.

Comparative Examples 6 to 9

Using the ethylene glycol dispersions prepared in Comparative Examples 1to 5, polyester films were prepared in the above-mentioned manner andproperties were evaluated. However, the ethylene glycol dispersionprepared in Comparative Example 3 contained a large amount of water andbumped, and thus the evaluation of a film was not conducted.

Reference Example 1

Inorganic particles U surface-treated was obtained in the same manner asin Example 1, and the inorganic particles and water were stirredvigorously and mixed to thus prepare a water slurry having a solidconcentration of 50% by weight. With this slurry, ethylene glycol in thepredetermined amount was mixed and water was removed by the use of anevaporator to thus obtain an ethylene glycol dispersion of the inorganicparticles U. Using the glycol dispersion obtained, a polyester film wasformed in the same manner as in Example 5. The evaluation results areshown in Table 4.

Reference Example 2

Inorganic particles V surface-treated was obtained in the same manner asin Example 2, and the inorganic particles and water were stirredvigorously and mixed to thus prepare a water slurry having a solidconcentration of 50% by weight. With this slurry, ethylene glycol in thepredetermined amount was mixed and water was removed by the use of anevaporator to thus obtain an ethylene glycol dispersion of the inorganicparticles V. Using the glycol dispersion obtained, a polyester film wasformed in the same manner as in Example 6. The evaluation results areshown in Table 4.

From the comparison with Reference Examples 1 and 2, it is understoodthat the ethylene glycol dispersions obtained in Examples 1 to 4 and 9do not require a large amount of energy and that they provide filmshaving excellent properties identical to those of Reference Examples 1and 2.

TABLE 4 Evaluation results of polyester films Ethylene Surface glycolroughness Friction dispersions Ra coefficient Abrasion Abrasion Coarseused (μm) (μk) I II protrusions Ref. Ex. 1 — 0.018 0.15 b b 5th classRef. Ex. 2 — 0.013 0.14 a a 5th class Example 5 Example 1 0.018 0.15 b b5th class Example 6 Example 2 0.013 0.14 a a 5th class Example 7 Example3 0.018 0.15 b b 5th class Example 8 Example 4 0.020 0.16 b b 4th classExample 10 Example 9 0.017 0.15 b b 5th class Comp. Ex. 6 Comp. Ex. 10.028 0.15 d c 1st class Comp. Ex. 7 Comp. Ex. 2 0.029 0.15 c c 2ndclass Comp. Ex. 8 Comp. Ex. 4 0.033 0.15 d c 1st class Comp. Ex. 9 Comp.Ex. 5 0.033 0.16 d c 1st class

Industrial Applicability

As stated above, according to the present invention, it is possible totransport in the form of powder and to make a glycol dispersion at afactory where they are used so that a drastic simplification in theproduction steps and a cost reduction are attainable because neither adistillation apparatus for replacing a solvent such as water andmethanol with glycol nor a step of wet- pulverizing is required.Moreover, it is possible to make a glycol dispersion by dispersing inglycol the inorganic powder with the particle shape and size maintainedbefore drying or in the initial state, and as a result, it is possibleto provide a polyester composition containing the glycol dispersion ofan inorganic powder uniformly dispersed therein.

What is claimed is:
 1. A glycol dispersion of an inorganic powder whichcomprises glycol and an inorganic powder dispersed therein, saidinorganic powder being surface-treated with a dispersant other thanglycol having a solubility of not less than 5 (g/100 g water) in waterof 20° C., and which contains water and/or methanol in a range tosatisfy the following equations (1) to (3): 1≦A≦20/t  (1) 0.5≦B≦10  (2)5≦C  (3) wherein A: % by weight of water and/or methanol based on theinorganic powder t: % by weight of the dispersant based on the inorganicpowder B: % by weight of water and/or methanol in the glycol dispersionC: % by weight of the inorganic powder in the glycol dispersion.
 2. Theglycol dispersion of an inorganic powder of claim 1, wherein thedispersant is selected from the group consisting of alkali metal saltsof condensed phosphoric acids, alkali metal salts of alicyclic oraromatic resin acids, sulfonic acid-containing compounds, sulfuricacid-containing compounds, phosphoric acid-containing compounds, esters,salts of alkali metals, ammonium and amine of said acid-containingcompounds, cellulose-containing compounds, unsaturated carboxylic acids,polymers of unsaturated carboxylic acids and copolymers of unsaturatedcarboxylic acids and monomers copolymerizable therewith, and partiallyor completely neutralized polymers of unsaturated carboxylic acids andcopolymers of unsaturated carboxylic acids and monomers copolymerizabletherewith.
 3. The glycol dispersion of an inorganic powder of claim 1,wherein the inorganic powder is at least one selected from the groupconsisting of calcium carbonate, titanium dioxide, silica, talc, kaolinand calcium phosphate.
 4. The glycol dispersion of an inorganic powderof claim 3, wherein the dispersant is selected from the group consistingof alkali metal salts of condensed phosphoric acids, alkali metal saltsof alicyclic or aromatic resin acids, sulfonic acid-containingcompounds, sulfuric acid-containing compounds, phosphoricacid-containing compounds, esters, salts of alkali metals, ammonium andamine of said acid-containing compounds, cellulose-containing compounds,unsaturated carboxylic acids, polymers of unsaturated carboxylic acidsand copolymers of unsaturated carboxylic acids and monomerscopolymerizable therewith, and partially or completely neutralizedpolymers of unsaturated carboxylic acids and copolymers of unsaturatedcarboxylic acids and monomers copolymerizable therewith.
 5. A polyestercomposition containing the glycol dispersion of an inorganic powderdefined in claim
 1. 6. The polyester composition of claim 5, wherein thedispersant is selected from the group consisting of alkali metal saltsof condensed phosphoric acids, alkali metal salts of alicyclic oraromatic resin acids, sulfonic acid-containing compounds, sulfuricacid-containing compounds, phosphoric acid-containing compounds, esters,salts of alkali metals, ammonium and amine of said acid-containingcompounds, cellulose-containing compounds, unsaturated carboxylic acids,polymers of unsaturated carboxylic acids and copolymers of unsaturatedcarboxylic acids and monomers copolymerizable therewith, and partiallyor completely neutralized polymers of unsaturated carboxylic acids andcopolymers of unsaturated carboxylic acids and monomers copolymerizabletherewith.
 7. The glycol dispersion of an inorganic powder of claim 1,wherein the following equation (4) is satisfied: 3Y≦X≦30Y  (4) whereinX: % by weight of water and/or methanol added into the glycol dispersionY: % by weight of water adsorbed onto the inorganic powder.
 8. Apolyester composition containing the glycol dispersion of an inorganicpowder defined in claim
 7. 9. A method for producing a glycol dispersionof an inorganic powder which comprises the following steps of:surface-treating an inorganic powder with a dispersant other than glycolhaving a solubility of not less than 5 (g/100 g water) in water of 20°C., and dispersing the surface-treated inorganic powder in glycoltogether with water and/or methanol so as to satisfy the followingequations (1) to (3): 1≦A≦20/t  (1) 0.5≦B≦10  (2) 5≦C  (3)  wherein A: %by weight of water and/or methanol based on the inorganic powder t: % byweight of the dispersant based on the inorganic powder B: % by weight ofwater and/or methanol in the glycol dispersion C: % by weight of theinorganic powder in the glycol dispersion.
 10. The method of claim 9,wherein the dispersant is selected from the group consisting of alkalimetal salts of condensed phosphoric acids, alkali metal salts ofalicyclic or aromatic resin acids, sulfonic acid-containing compounds,sulfuric acid-containing compounds, phosphoric acid-containingcompounds, esters, salts of alkali metals, ammonium and amine of saidacid-containing compounds, cellulose-containing compounds, unsaturatedcarboxylic acids, polymers of unsaturated carboxylic acids andcopolymers of unsaturated carboxylic acids and monomers copolymerizabletherewith, and partially or completely neutralized polymers ofunsaturated carboxylic acids and copolymers of unsaturated carboxylicacids and monomers copolymerizable therewith.
 11. The method forproducing a glycol dispersion of an inorganic powder of claim 9, whereinthe following equation (4) is satisfied: 3Y≦X≦30Y  (4) wherein X: % byweight of water and/or methanol added into the glycol dispersion Y: % byweight of water adsorbed onto the inorganic powder.